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Current demand of battery charger?

Discussion in 'General Electronics' started by Patrik, Aug 4, 2003.

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  1. Patrik

    Patrik Guest


    I'm designing a battery charger for NiMh cells, four of them to be
    exact. One way of designing this is to use _one_ current source that
    feeds all four cells that are connected in series. Another way of
    design is using four separate current sources, on for each cell. This
    second way seems most interresting because of the capability to
    measure the temperature of each cell and stop loading just the actual
    cell that is fully charged.
    I decided to load invidually, and began to think about how much
    current this charger will require.
    Say I use only one current source, set to 1.5 ampere. The charger then
    needs just 1.5A, and the GP2000 cells will be fully charged in
    (estimated) 1 hour and a half.
    Say instead I use four parallel current sources, set to 1.5A. The
    charger then needs 6A, and the GP2000 cells will be fully charged in
    (again estimated) 1.5 hour.


    This doesn't seem correct, can somebody please tell me what is

    Regards Patrik
  2. (Patrik) wrote in message
    First of all, I am new in electronics as well but I think I can help
    you. You are correct in the way you are looking at the current draw.
    One thing that might help you is if you look at the total input watts
    in each case. In each case the Volts times the Amps is the same. So
    the same power is applied in both cases. Using the lower voltage,
    higher amperage meathod may make it harder to build an efficient power
    supply, but if the efficiency of the power supply in both cases is
    constant, the same power will be drawn from the source.

    Hope that helps
  3. Gary Lecomte

    Gary Lecomte Guest

    Yes, that is correct.
    And charging at that rate, it is really important to monitor
    temperature or better yet the point at which the cell voltage starts
    to decline after increasing to peak.

    Take care...Gary
  4. Rich Grise

    Rich Grise Guest

    (Patrik) wrote in message > Hello
    What doesn't seem correct about it? 1.5 + 1.5 + 1.5 + 1.5 = 6, after all. : )

  5. Rich Grise

    Rich Grise Guest

    (Patrik) wrote in message
    Imagine a sort of trough, or channel, full of ping-pong balls. (single-
    file). At the end, they fall off and into a bucket. Say it takes 100
    ping-pong balls to fill one bucket. Simple enough, right? So, now,
    add 3 buckets, and put a fork in the channel, so you're filling up
    four buckets. How many ping-pong balls do you need?

    Good Luck!
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